Occultic;Nine - End
All said a pretty good ending, but still left a lot to be desired.
Some things never got fully answered or explained (the vanguard kid, the emperor, Ririka, etc.). I don't mind an open ending, but some more explanations would've been nice. In the end, some characters still never felt fully developed, and didn't get as much time in the sun as they should've. Frankly, in some ways the ending felt like a tease for the VN (want all the answers? want the real good ending? Play the game!).
I'd say it probably needed another episode to fully explore all the stuff in the last episode.
I maintain that this reads better as a LN and probably a VN. The LN does a much better job of developing the characters, giving them all time to do stuff, foreshadowing, and explaining things as it goes, but then again it also doesn't have the pacing issues of the anime.
All that said, I did find Occultic;Nine an enjoyable ride. There was intrigue and some good foreshadowing throughout. It all just needed more space to breathe. I wouldn't readily recommend the anime, but I would say keep an eye on the VN and check out the LN.